Electroluminescence (EL) is a phenomenon where a material emits light in response to an electric voltage/current or in response to a strong electric field. EL is the result of radiative recombination of electrons and holes in a material (usually a semiconductor).
Excited electrons release their energy as photons, for example visible light. Prior to recombination, electrons and holes are separated either as a result of doping of the material to form a p-n junction (in semiconductor electroluminescent devices such as LEDs), or through excitation by impact of high-energy electrons accelerated by a strong electric field (as with the phosphors in electroluminescent displays).
There have been a number of recent developments in electroluminescent (EL) devices for use in light emissive displays, including the use of organic polymers. EL devices containing an organic polymer generally have the following configuration: anode/organic polymer/EL material/cathode. The anode is typically any material that has the ability to inject holes into the EL material, such as, for example, indium/tin oxide (ITO). Optionally, the anode may be supported on a glass or plastic substrate. EL materials include, for example, fluorescent dyes, fluorescent and phosphorescent metal complexes, conjugated polymers, and mixtures thereof. The cathode is typically any material, such as Calcium (Ca) or Barium (Ba), that has the ability to inject electrons into the EL material. The organic polymer is typically a conductive organic polymer which facilitates the injection of holes from the anode into the EL polymer component. Stress-induced light emitting materials emit light in response to application of a mechanical stress.